1. Field of the Invention
The present invention relates to digital broadcast receiving apparatuses and digital broadcast apparatuses for receiving and transmitting transport streams onto which video data and/or audio data are multiplexed.
2. Description of the Related Art
In addition to broadcast programs constituted by video data and audio data, data programs are also broadcasted through digital TV broadcast systems. These programs are broadcasted by being multiplexed onto transport streams. Various kinds of information are concurrently multiplexed onto a transport stream and broadcasted so that these programs can be received by a receiving apparatus. These pieces of information are repeatedly broadcasted as tables in a section format. The examples are written in ETSI EN 300 468 (page 12, FIG. 2).
For example, in the DVB (Digital Video Broadcasting) standard, which is prominent as a digital broadcast system used in Europe, various tables are broadcast, such as a PAT (Program Association Table), a PMT (Program Map Table), and a CAT (Conditional Access Table) which are defined according to the MPEG2 (Moving Picture Experts Group 2) standard as PSI (Program Specific Information) (cf. ISO/IEC 13818-1, page 41, Chapter 2.4.4.), as well as an NIT (Network Information Table), an SDT (Service Description Table), an EIT (Event Information Table), a TOT (Time Offset Table), and a TDT (Time and Date Table), each of which are defined as SI (Service Information) (cf. ISO/IEC 13818-1, page 41, Table 2-25), and so on.
These tables are separated and extracted from transport streams and are stored into a memory so that they can be used for tuning of programs, switching between audio and video, displaying EPGs, and the like.
The technique for separating and extracting these tables is disclosed in, for example, the Japanese Unexamined Patent Application Publication No. 11-112897. A plurality of filters are used in such separation and extraction. The examples are cited, for example, in “Denshi Gijutsu” (Vol. 42, No. 9, page 24, Table 2 (2000)).
As the broadcast of a program proceeds, these tables are updated. A version number is attached to each table. The version number of a table being separated and extracted is compared with the version number of the table stored in a memory. When the version numbers are the same, the table will be discarded. When it is found that the table has been updated, what is stored in the memory will be updated. Thus, it is necessary to have a large number of filters available in order to regularly separate and extract tables.
In addition, when a table becomes unnecessary and stops being multiplexed onto transport streams and being broadcast, the unnecessary table will be stored in the memory permanently, and fills up the memory in vain, because it is not possible to separate and extract that table using the filter assigned for separation and extraction of the table.